1. Field of the Invention
The present invention relates to portable terminals, such as cellular phones, Personal Digital Assistants (PDAs), hand held phones, MP3 phones, game phones, camera phones, internet phones, combinations of these devices, and the like. More particularly, the present invention relates to a sliding device for a sliding type portable terminal which includes a sliding module capable of sliding a sliding housing in multiple steps.
2. Description of the Related Art
In general, a “portable terminal” is an electronic device which a user can carry to wirelessly communicate with another user. Conventional portable terminals may be classified into various types according to their appearance, such as bar type portable terminals, flip type portable terminals, and folder type portable terminals. A bar type portable terminal has a single housing shaped like a bar. A flip type portable terminal has a flip panel which is pivotally mounted to a bar-shaped housing by a hinge unit. A folder type portable terminal has a folder coupled to a single bar-shaped housing by a hinge unit in such a manner that the folder can be rotated in order to be folded or unfolded from the housing.
Portable terminals may also be classified as neck-wearable type terminals or wrist-wearable type terminals, according to the position at or the way in which a user wears the terminal. In addition, portable terminals may be classified into swing type terminals, sliding type terminals, and sliding-swing type terminals. These various classifications are well understood by those skilled in the art.
As shown in FIGS. 1 to 5, a sliding type portable terminal 1 includes a body housing 2 having a plurality of keypads 2a and a microphone unit 2b arranged thereon, and a sliding housing 3 which can slide along the body housing 2 to a position corresponding to about one-third of the entire length of the body housing. Generally, the body housing 2 has a 3×4 matrix keypad arranged thereon. The sliding housing 3 includes an auxiliary keypad on which a plurality of auxiliary keys are arranged, a speaker unit 3a, and a display unit 3b. 
As shown in FIGS. 3 and 4, the conventional sliding type portable terminal 1 includes a body housing 2, a sliding housing that slides on the body housing 2 by a predetermined distance, a sliding module 4 disposed between the body housing 2 and the sliding housing 3 for enabling the sliding housing 3 to slide on the body housing, and at least one coil spring 5 provided between the sliding housing 3 and the body housing 2 for supplying elasticity to the sliding housing to assist the sliding movement of the sliding housing on the body housing.
As shown in FIGS. 3 and 4, the sliding module 4 includes a main plate 4a provided in the body housing 2 and a sliding plate 4b provided in the sliding housing 3.
As shown in FIG. 5, the sliding module of the conventional portable terminal has a structure in which the coil spring causes the sliding housing to slide on the body housing to a position at which the sliding movement of the sliding housing is completed. When the sliding housing is repeatedly moved, the elasticity of the coil spring may degrade. Further, the sliding module does not provide a tactile sensation (such as a click) when the sliding housing slides on the body housing. Thus, a user may not fully appreciate the sliding movement of the sliding housing.
Further, the sliding module of the conventional portable terminal can enable the sliding housing to slide on the body housing only in one longitudinal direction of the portable terminal, so as to open the sliding housing by about one-third of the entire length of the body housing. Thus, there is a disadvantage in that it is impractical to use the remaining, non-opened space on the body housing of the portable terminal, and optimal use of space in the portable terminal is impeded.
Accordingly, there is a need for an improved sliding device for a portable terminal.